The overall aim of this revised competing continuation of an Independent Scientist Award is to continue the development of the principal investigator as a clinical scientist. The focus of research for the P.I. is the neurobiology of impulse control as it relates to initiation and maintenance of substance abuse. During the initial 5 years of funding, the principal investigator, F. Gerard Moeller, M.D., developed his expertise in the area of impulsivity, serotonin and substance abuse. The overall goals of this application will be to extend the understanding of impulse control and substance abuse developed through the initially funded Independent Scientist Award with new techniques and collaborations. Once the underlying neurobiology of these behaviors is determined, this will allow development of treatments for impulsivity, which leads to behaviors such as drug abuse or impulsive sexual behaviors that increase the risk for HIV transmission. The primary focus of this application will be to gain additional training in basic and behavioral techniques related to brain imaging in substance dependent subjects. This will be accomplished through two primary short term goals: 1) To obtain additional training in functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) as they relate to impulse control in substance abuse. 2) To develop behavioral techniques for use in brain imaging to measure activation of key brain regions related to impulse control and substance abuse, including the prefrontal cortex and amygdala. In addition to the primary aims of this independent scientist award, there are two secondary aims: 1) to develop tools to examine the role of impulsivity in risky sexual behavior as a risk factor for HIV infection. 2) To develop the investigator as a mentor of junior Psychiatrists who are interested in a career in substance abuse research. The long-term goal of this application is to develop the principal investigator as a senior scientist with the expertise to bridge the gap between basic behavioral science, neurobiology, and treatment in substance abuse. The research plan draws heavily from R01DA15345, and the competing renewal of R01DA08425, on which the author is the principal investigator.